The present invention relates generally to a system including a locating arrangement for tracking a boring tool and one or more buried lines such as, for example, pipes, cables, conduits or other conductors and, more particularly, to a locating arrangement configured for receiving a boring tool locating signal and at least one cable locating signal for determining at least one scaled positional relationship based, at least in part, on the received locating signals.
The installation of utility lines underground is increasingly popular for reasons of aesthetics and for practical reasons such as, for example, protecting these lines from the effects of severe above ground weather conditions. In areas where buried lines have previously been installed, however, it is undesirable to excavate an entire pathway for the purpose of installing additional lines since such excavation many times results in the unintentional damage of an existing utility line. Areas which include buried fiber optic cables are particularly problematic for several reasons. First, a fiber optic cable is difficult to repair once it has been severed or damaged. Second, because a fiber optic cable is capable of simultaneously carrying a vast amount of information, downtime can be quite costly.
In the past, various horizontal drilling systems, including locating and monitoring systems, have been developed which advantageously eliminate the need for excavating the entire pathway in which a utility line is to be installed. The attendant locating and monitoring systems serve in tracking the position of the boring tool and may further serve in tracking the position of one or more buried obstacles such as, for example, utility lines. While these prior art systems are generally suited for their intended purpose, it is submitted that a majority of prior art approaches do not integrate boring tool and cable locating data. That is, the prior art generally views cable locating and boring tool tracking as entirely separate activities wherein, for example, a handheld portable locator operates in a selected one of a cable locating mode or a boring tool tracking mode. See, for example, a conference paper describing a cable locating technique based on the so-called gradient method as reported by C. A. Young (“Measuring the depth of buried cables”, Bell Laboratories Record, Vol. 43, No. 10, November 1965).
One approach that does integrate cable and boring tool locating signal data is described in copending U.S. patent application Ser. No. 09/641,006, entitled FLUX PLANE LOCATING IN AN UNDERGROUND DRILLING SYSTEM which is commonly assigned with the present application and which is incorporated herein by reference. While this approach is highly effective and provides sweeping advantages over the state-of-the-art as of its filing date, it is submitted that still further enhancements are possible.
Another concern with regard to the prior art resides in locator configurations useful in depth determination of buried cables. In particular, the prior art locator includes a wand which extends below the locator when held by an operator. A lowermost end of the wand may be placed on the surface of the ground during a depth measurement. The configuration of the wand includes antennas at spaced apart positions within the extension of the wand and directed to the task of depth determination. It is submitted that the need for the wand provides a locator having an unwieldy, oversized configuration. See, for example, a technical paper entitled “Alternating Magnetic Field technology for Locating Buried Utility Lines and for Providing Information for No Dig Techniques”, presented in April 1985 at the NO Dig Conference in London, UK, showing a “wand” locator configured for a 2 point height determination having separate, spaced apart antennas in the wand.
The present invention provides a highly advantageous enhanced locating arrangement and associated method configured for cable and boring tool locating in a way that has heretofore been unknown and which provides still further advantages, for example, related to cable depth determination, as will be described.